Tumor Vaccines

A Three-in-One Immunotherapy Nanoweapon via Cascade-Amplifying Cancer-Immunity Cycle against Tumor Metastasis, Relapse, and Postsurgical Regrowth

The antitumor immune response involves a cascade of three phases, namely, antigen presentation (Phase I), lymphocyte activation and proliferation/differentiation (Phase II), and tumor elimination (Phase III). Therefore, an ideal immunotherapy nanoplatform is one that can simultaneously execute these three phases. However, it is of great challenge to develop a single immunotherapy nanoplatform which can deliver individual immunoagent to their on-demand target sites for simultaneously tailoring three phases because of the different target sites restricted by three phases. Herein, for the first time we reported a three-in-one immunotherapy nanoplatform that can simultaneously execute these three phases. Chlorin e6 (Ce6)-conjugated hyaluronic acid (HC), dextro-1-methyl tryptophan (1-mt)-conjugated polylysine (PM) and anti-PD-L1 monoclonal antibodies (aPD-L1) were rationally designed as aPD-L1@HC/PM NPs via an assembling strategy. The step-by-step detachment of the antigen from near-infrared light irradiated HC component, the indoleamine-pyrrole 2,3-dioxygenase (IDO) pathway inhibitor 1-mt, and the anti-PD-L1 toward their on-demand target sites demonstrated the simultaneous tailoring of Phase I, Phase II, and Phase III, respectively, of the immunotherapy. The aPD-L1@HC/PM NPs were verified to be an excellent immunotherapy nanoplatform against tumor metastasis, relapse, and postsurgical regrowth because of the cascade-amplifying cancer-immunity cycle. The present all-immunity-phase-boosted immunotherapy strategy is of great interest for designing excellent immunotherapy treatments.

The immunosuppressive tumor environment is the major impediment to successful therapeutic vaccination in Neu transgenic mice

We earlier showed that therapeutic vaccination of FVB/N mice with alphaviral replicon particles expressing rat neuET-VRP induced regression of established neu-expressing tumors. In this study, we evaluated the efficacy of neuET-VRPs in a tolerant mouse model using mice with transgenic expression of neu. Using the same approach that induced regression of 70 mm(2) tumors in FVB/N mice, we were unable to inhibit tumor growth in tolerant neu-N mice, despite showing neu-specific B-cell and T-cell responses post vaccination. As neu-N mice have a limited T-cell repertoire specific to neu, we hypothesized that the absence of these T cells led to differences in the vaccine response. However, transfer of neu-specific T cells from vaccinated FVB/N mice was not effective in inducing tumor regression, as these cells did not proliferate in the tumor-draining lymph node. Vaccination given with low-dose cyclophosphamide to deplete regulatory T cells delayed tumor growth but did not result in tumor regression. Finally, we showed that T cells given with vaccination were effective in inhibiting tumor growth, if administered with approaches to deplete myeloid-derived suppressor cells. Our data show that both central deletion of lymphocytes and peripheral immunosuppressive mechanisms are present in neu-N mice. However, the major impediment to successful vaccination is the peripheral tumor-induced immune suppression.

DNA vaccines: developing new strategies against cancer

Due to their rapid and widespread development, DNA vaccines have entered into a variety of human clinical trials for vaccines against various diseases including cancer. Evidence that DNA vaccines are well tolerated and have an excellent safety profile proved to be of advantage as many clinical trials combines the first phase with the second, saving both time and money. It is clear from the results obtained in clinical trials that such DNA vaccines require much improvement in antigen expression and delivery methods to make them sufficiently effective in the clinic. Similarly, it is clear that additional strategies are required to activate effective immunity against poorly immunogenic tumor antigens. Engineering vaccine design for manipulating antigen presentation and processing pathways is one of the most important aspects that can be easily handled in the DNA vaccine technology. Several approaches have been investigated including DNA vaccine engineering, co-delivery of immunomodulatory molecules, safe routes of administration, prime-boost regimen and strategies to break the immunosuppressive networks mechanisms adopted by malignant cells to prevent immune cell function. Combined or single strategies to enhance the efficacy and immunogenicity of DNA vaccines are applied in completed and ongoing clinical trials, where the safety and tolerability of the DNA platform are substantiated. In this review on DNA vaccines, salient aspects on this topic going from basic research to the clinic are evaluated. Some representative DNA cancer vaccine studies are also discussed.

Cellular immunotherapy of cancer

Standard therapies for many common cancers remain toxic and are often ineffective. Cellular immunotherapy has the potential to be a highly targeted alternative, with low toxicity to normal tissues but a high capacity to eradicate tumor. In this chapter we describe approaches that generate cellular therapies using active immunization with cells, proteins, peptides, or nucleic acids, as well as efforts that use adoptive transfer of effector cells that directly target antigens on malignant cells. Many of these approaches are proving successful in hematologic malignancy and in melanoma. In this chapter we discuss the advantages and limitations of each and how over the next decade investigators will attempt to broaden their reach, increase their efficacy, and simplify their application.

DNA vaccination induces WT1-specific T-cell responses with potential clinical relevance

The Wilms tumor antigen, WT1, is associated with several human cancers, including leukemia. We evaluated WT1 as an immunotherapeutic target using our proven DNA fusion vaccine design, p.DOM-peptide, encoding a minimal tumor-derived major histocompatibility complex (MHC) class I–binding epitope downstream of a foreign sequence of tetanus toxin. Three p.DOM-peptide vaccines, each encoding a different WT1-derived, HLA-A2–restricted epitope, induced cytotoxic T lymphocytes (CTLs) in humanized transgenic mice expressing chimeric HLA-A2, without affecting hematopoietic stem cells. Mouse CTLs killed human leukemia cells in vitro, indicating peptide processing/presentation. Low numbers of T cells specific for these epitopes have been described in cancer patients. Expanded human T cells specific for each epitope were lytic in vitro. Focusing on human WT137–45–specific cells, the most avid of the murine responses, we demonstrated lysis of primary leukemias, underscoring their clinical relevance. Finally, we showed that these human CTL kill target cells transfected with the relevant p.DOM-peptide DNA vaccine, confirming that WT1-derived epitopes are presented to T cells similarly by tumors and following DNA vaccination. Together, these data link mouse and human studies to suggest that rationally designed DNA vaccines encoding WT1-derived epitopes, particularly WT137–45, have the potential to induce/expand functional tumor-specific cytotoxic responses in cancer patients.

Dendritic cells pulsed with alpha-fetoprotein and mutant P53 fused gene induce bi-targeted cytotoxic T lymphocyte response against hepatic carcinoma

Dendritic cell (DC)-based immunotherapy is rapidly emerging as a promising treatment in cancer therapy. We had previously shown that DC pulsed with either defined mRNA of tumor antigen (Ag) such as alpha-fetoprotein (AFP), or total RNA of hepatocellular carcinoma (HCC) could elicit Ag-specific cytotoxic T lymphocyte (CTL) response. Therefore, we suggested a novel DC-based therapeutic method, in which DCs derived from CD34(+) cells enriched peripheral blood mononuclear cells were pulsed with liposome-coated AFP and mutant P53 (mtP53) fused gene pEGFP-C3/AFP-mtP53 to induce bi-targeted specific CTL responses against HCC. Three different genotype HCC cell lines, HepG2 (human histocompatibility leukocyte antigens (HLA) A2 positive, AFP expressing positive, P53 expressing negative), SMMC7721 (HLA A2 positive, neither AFP nor P53 expressing positive), and HMCC97 (HLA A2 positive, both AFP and P53 expressing positive) were selected as targets for CTL responses. An important finding was that DCs pulsed with the liposome-coated fused gene could evoke more intensive bi-targeted Ag-specific CTL responses against HMCC97 than DCs pulsed with either AFP or P53 single gene (P < 0.05). This experimental therapeutic model provides a new promising cytotherapeutic approach, in that DCs pulsed with the fused gene of different Ags might induce more extensive multitargeted antitumor immunity.

DNA vaccines: precision tools for activating effective immunity against cancer

DNA vaccination has suddenly become a favoured strategy for inducing immunity. The molecular precision offered by gene-based vaccines, together with the facility to include additional genes to direct and amplify immunity, has always been attractive. However, the apparent failure to translate operational success in preclinical models to the clinic, for reasons that are now rather obvious, reduced initial enthusiasm. Recently, novel delivery systems, especially electroporation, have overcome this translational block. Here, we assess the development, current performance and potential of DNA vaccines for the treatment of cancer.

A DNA fusion vaccine induces bactericidal antibodies to a peptide epitope from the PorA porin of Neisseria meningitidis

An experimental DNA plasmid vaccine was developed based on a well-characterized and protective peptide epitope derived from a bacterial porin protein. For this study, we used the P1.16b serosubtype epitope, located in variable region (VR)2 in loop 4 of the PorA outer membrane (OM) porin from Neisseria meningitidis serogroup B strain MC58. A plasmid that encoded the entire loop (pPorAloop4) was prepared, as well as a fusion plasmid that encoded the loop in tandem with the fragment C (FrC) immunostimulatory sequence from tetanus toxin (pPorAloop4-FrC). The constructs were used for intramuscular immunization without exogenous adjuvant. Murine antisera raised to the pPorAloop4-FrC DNA fusion plasmid reacted significantly with OMs in enzyme-linked immunosorbent assay and with whole bacteria by immunofluorescence, whereas antisera raised to the pPorAloop4 DNA plasmid and to control plasmid showed little or no reactivity. Significantly, only the pPorALoop4-FrC plasmid induced bactericidal antibodies, demonstrating that the intrinsic immunostimulatory sequence was essential for inducing a protective immune response. The antibodies raised to the P1.16b pPorALoop4-FrC plasmid were serosubtype specific, showing no significant immunofluorescence reactivity or bactericidal activity against other PorA variants. These data provide proof of principle for a DNA fusion plasmid strategy as a novel approach to preparing vaccines based on defined, protective epitopes.

Comparative prime-boost vaccinations using Semliki Forest virus, adenovirus, and ALVAC vectors demonstrate differences in the generation of a protective central memory CTL response against the P815 tumor

Tumor-specific Ags are potential target molecules in the therapeutic treatment of cancer. One way to elicit potent immune responses against these Ags is to use recombinant viruses, which activate both the innate and the adaptive arms of the immune system. In this study, we have compared Semliki Forest virus (SFV), adenovirus, and ALVAC (poxvirus) vectors for their capacity to induce CD8(+) T cell responses against the P1A tumor Ag and to elicit protection against subsequent challenge injection of P1A-expressing P815 tumor cells in DBA/2 mice. Both homologous and heterologous prime-boost regimens were studied. In most cases, both higher CD8(+) T cell responses and better tumor protections were observed in mice immunized with heterologous prime-boost regimens, suggesting that the combination of different viral vectors is beneficial for the induction of an effective immune response. However, homologous immunization with SFV provided potent tumor protection despite a rather moderate primary CD8(+) T cell response as compared with mice immunized with recombinant adenovirus. SFV-immunized mice showed a rapid and more extensive expansion of P1A-specific CD8(+) T cells in the tumor-draining lymph node after tumor challenge and had a higher frequency of CD62L(+) P1A-specific T cells in the blood, spleen, and lymph nodes as compared with adenoimmunized mice. Our results indicate that not only the magnitude but in particular the quality of the CD8(+) T cell response correlates with tumor protection.

DNA fusion vaccines induce epitope-specific cytotoxic CD8(+) T cells against human leukemia-associated minor histocompatibility antigens

The graft-versus-leukemia effect of allogeneic stem-cell transplantation is believed to be mediated by T-cell recognition of minor histocompatibility antigens on recipient cells. For minor histocompatibility antigens HA-1 and HA-2, normal cell expression is restricted to hemopoietic cells, and boosting the immune response to these antigens may potentiate graft-versus-leukemia effect without accompanying graft-versus-host disease. To increase efficacy, expansion of HA-1- or HA-2-specific CTL before transplantation is desirable. However, primary HA-1- or HA-2-specific CTL expanded in vitro are often of low avidity. An alternative approach is to prime specific CTL responses in vivo by vaccination. Clearly, donor vaccination must be safe and specific. We have developed DNA fusion vaccines able to induce high levels of epitope-specific CTL using linked CD4(+) T-cell help. The vaccines incorporate a domain of tetanus toxin (DOM) fused to a sequence encoding a candidate MHC class I binding peptide. This design generates antitumor CD8(+) T-cell responses and protective immunity in preclinical models. For clinical application, we constructed vaccines encoding HLA-A*0201-restricted peptides from human HA-1 and HA-2, which were fused to DOM, and tested their performance in HLA-A*0201-transgenic mice. Priming induced epitope-specific, IFNgamma-producing CD8(+) T cells with cytotoxic function boosted to high levels with electroporation. Strikingly, these mouse T cells efficiently killed human lymphoblastoid cell lines expressing endogenous HA-1 or HA-2. High avidity is indicated by the independence of cytolysis from CD8/MHC class I interaction. These safe epitope-specific vaccines offer a potential strategy to prime HA-1- or HA-2-specific CTL in transplant donors before adoptive transfer.

T-cell receptor-like antibodies: novel reagents for clinical cancer immunology and immunotherapy

Major histocompatibility complex class I molecules play a central role in the immune response against a variety of cells that have undergone malignant transformation by shaping the T-cell repertoire and presenting peptide antigens from endogeneous antigens to CD8+ cytotoxic T-cells. Diseased tumor or virus-infected cells are present on class I major histocompatibility complex molecule peptides that are derived from tumor-associated antigens or viral-derived proteins. Due to their unique specificity, such major histocompatibility complex-peptide complexes are a desirable target for novel approaches in immunotherapy. Targeted delivery of toxins or other cytotoxic drugs to cells which express specific major histocompatibility complex-peptide complexes that are involved in the immune response against cancer or viral infections would allow for a specific immunotherapeutic treatment of these diseases. It has recently been demonstrated that antibodies with the antigen-specific, major histocompatibility complex-restricted specificity of T-cells can be generated by taking advantage of the selection power of phage display technology. In addition to their tumor targeting capabilities, antibodies that mimic the fine specificity of T-cell receptors can serve as valuable research reagents that enable study of human class I peptide-major histocompatibility complex ligand presentation, as well as T-cell receptor peptide-major histocompatibility complex interactions. T-cell receptor-like antibody molecules may prove to be useful tools for studying major histocompatibility complex class I antigen presentation in health and disease as well as for therapeutic purposes in cancer, infectious diseases and autoimmune disorders.

Update on cancer vaccines

PURPOSE OF REVIEW

Vaccination against cancer has had a variable history, with claims of success often fading into disappointment. The reasons for this include poor vaccine design, inadequate understanding of the nature of the immune response, and a lack of objective measures to evaluate performance. The impact of genetic technology has changed everything. We now have multiple strategies to identify candidate tumor antigens, and we understand more about activation and regulation of immunity against cancer. There are novel vaccine strategies to activate specific attack on tumor cells. We also have modern assays using surrogate markers of performance to correlate with clinical effects. It is timely to select significant relevant papers to illustrate the growing potential for patients with cancer.

RECENT FINDINGS

Recent findings include tumor antigen discovery and vaccine formulation, relevant knowledge concerning mechanisms of induction of effective immunity from preclinical models, and translation into clinical trials with objective evaluation of performance.

SUMMARY

The ability of the immune response to dispose of cancer cells is clear. Passive transfer of antibody or immune cells is already clinically successful. We are now in a position to harness new gene-based information to design vaccines capable of inducing effective and long-lasting immunity. Safe vaccines could be used either in patients or in transplant donors. Pilot clinical trials are the means of testing performance, with continuing vaccine design modification to target specific antigens in different cancers.

T cell-mediated immunotherapy of metastases: state of the art in 2005

Advances in cellular and molecular immunology have led to the development of strategies for effective augmentation of antitumour immune responses in cancer patients. This review focuses on the manipulation of T cell immunity either by active specific immunotherapy (ASI) using tumour vaccines, or by adoptive immunotherapy (ADI) with immune T cells. Such therapies offer exquisite specificity of tumour recognition based on the ability of the T cell to distinguish single amino acid differences in any protein from any compartment of the tumour cell. Examples are presented of clinical survival benefits for cancer patients by postoperative ASI with a modified autologous tumour vaccine of high quality. Furthermore, clinical studies employing ADI with T cells activated and expanded ex vivo have demonstrated 'proof of principle' that tumour-specific T cells are capable of mediating anticancer activity in vivo, as measured by regression of metastatic tumours. Translation of these findings into a standardised immunotherapy is, however, not easy and will require coordination and cooperation among academic, private and federal sectors.

Computational modeling of the immune response to tumor antigens

Vaccination protocols designed to elicit anti-cancer immune responses have, many times, failed in producing tumor eradication and in prolonging patient survival. Usually in cancer vaccination, epitopes from one organism are included in the genome or linked with some protein of another in the hope that the immunogenic properties of the latter will boost an immune response to the former. However, recent results have demonstrated that injections of two different vectors encoding the same recombinant antigen generate high levels of specific immunity. Systematic comparison of the efficacy of different vaccination protocols has been hampered by technical limitations, and clear evidence that the use of multiple vectors has advantages over single carrier injections is lacking. We used a computational model to investigate the dynamics of the immune response to different anti-cancer vaccines based on randomly generated antigen/carrier compounds. The computer model was adapted for simulations to this new area in immunology research and carefully validated to the purpose. As a matter of fact, it reproduces a relevant number of experimental observations. The model shows that when priming and boosting with the same construct, competition rather than cooperation develops amongst T cell clones of different specificities. Moreover, from the simulations, it appears that the sequential use of multiple carriers may generate more robust anti-tumor immune responses and may lead to effective tumor eradication in a higher percentage of cases. Our results provide a rational background for the design of novel strategies for the achievement of immune control of cancer.

Electroporation as a "prime/boost" strategy for naked DNA vaccination against a tumor antigen

We have developed novel DNA fusion vaccines encoding tumor Ags fused to pathogen-derived sequences. This strategy activates linked T cell help and, using fragment C of tetanus toxin, amplification of anti-tumor Ab, CD4(+), and CD8(+) T cell responses is achievable in mice. However, there is concern that simple DNA vaccine injection may produce inadequate responses in larger humans. To overcome this, we tested electroporation as a method to increase the transfection efficiency and immune responses by these tumor vaccines in vivo in mice. Using a DNA vaccine expressing the CTL epitope AH1 from colon carcinoma CT26, we confirmed that effective priming and tumor protection in mice are highly dependent on vaccine dose and volume. However, suboptimal vaccination was rendered effective by electroporation, priming higher levels of AH1-specific CD8(+) T cells able to protect mice from tumor growth. Electroporation during priming with our optimal vaccination protocol did not improve CD8(+) T cell responses. In contrast, electroporation during boosting strikingly improved vaccine performance. The prime/boost strategy was also effective if electroporation was used at both priming and boosting. For Ab induction, DNA vaccination is generally less effective than protein. However, prime/boost with naked DNA followed by electroporation dramatically increased Ab levels. Thus, the priming qualities of DNA fusion vaccines, integrated with the improved Ag expression offered by electroporation, can be combined in a novel homologous prime/boost approach, to generate superior antitumor immune responses. Therefore, boosting may not require viral vectors, but simply a physical change in delivery, facilitating application to the cancer clinic.

Clinical Outcome of Lymphoma Patients After Idiotype Vaccination Is Correlated With Humoral Immune Response and Immunoglobulin G Fc Receptor Genotype

Purpose

The unique immunoglobulin idiotype (Id) expressed by each B-cell lymphoma is a target for immunotherapy. Vaccination with Id induces humoral and/or cellular anti-Id immune responses. However, the clinical impact of these anti-Id immune responses is unknown. We and others have previously reported that immunoglobulin G Fc receptor (FcγR) polymorphisms predict the clinical response of lymphoma patients to passive anti-CD20 antibody infusions. In this study, we tested whether anti-Id immune responses or FcγR polymorphisms associate with clinical outcome of patients who received Id vaccination.

Patients and Methods

We analyzed 136 patients with follicular lymphoma who had received Id vaccination. The anti-Id immune responses were measured and FcγRIIIa and FcγRIIa polymorphisms were determined and correlated with clinical outcome for these patients.

Results

Patients who mounted humoral immune responses had a longer progression-free survival (PFS) than those who did not (8.21 v 3.38 years; P = .018). Patients with FcγRIIIa 158 valine/valine (V/V) genotype also had a longer PFS than those with valine/phenylalanine (V/F) or phenylalanine/phenylalanine (F/F) genotypes (V/V, 8.21 v V/F, 3.38 years; P = .004; v F/F, 4.47 years; P = .035). Multivariate analysis using the Cox proportional hazards model showed that V/V genotype and humoral immune responses were independent positive predictors for PFS.

Conclusion

This study is the first to identify the predictive value of FcγR polymorphism on clinical outcome in patients who received active immunotherapy with tumor antigen vaccines. Our results imply that the antibodies induced against a tumor antigen are beneficial and that FcγR-bearing cells mediate an antitumor effect by killing antibody-coated tumor cells.

DNA vaccines to attack cancer

Delivery of antigens by injection of the encoding DNA allows access to multiple antigen-presenting pathways. Knowledge of immunological processes can therefore be used to modify construct design to induce selected effector functions. Expression can be directed to specific intracellular sites, and additional genes can be fused or codelivered to amplify responses. Therapeutic vaccination against cancer adds a requirement to overcome tolerance and to activate a weakened immune repertoire. Induction of CD4(+) T helper cells is critical for both antibody and T cell effector responses. To activate immunity against tumor antigens, we fused the tumor-derived sequences to genes encoding microbial proteins. This strategy engages T helper cells from the large antimicrobial repertoire for linked help for inducing antibody against cell-surface tumor antigens. The principle of linked T cell help also holds for induction of epitope-specific antitumor CD8(+) T cells, but the microbial sequence has to be minimized to avoid competition with tumor antigens. Epitope-specific DNA vaccination leads to powerful antitumor attack and can activate immunity from a profoundly tolerized repertoire. Vaccine designs validated in preclinical models are now in clinical trial with immune responses detected against both tumor antigens and fused microbial antigens. DNA priming is highly efficient, but boosting may benefit from increased antigen expression. Physical methods including electroporation provide increased expression without introducing additional competing antigens. A wide range of cancers can be targeted, and objective assays of response will determine efficacy.

DNA Fusion Vaccines Induce Targeted Epitope-Specific CTLs against Minor Histocompatibility Antigens from a Normal or Tolerized Repertoire

We have designed DNA fusion vaccines able to induce high levels of epitope-specific CD8(+) T cells, using linked CD4(+) T cell help. Such vaccines can activate effective immunity against tumor Ags. To model performance against minor histocompatibility (H) Ags important in allogeneic hemopoietic stem cell transplantation, responses against the H2D(b)-restricted Uty and Smcy male HY epitopes have been investigated. Vaccination of females induced high levels of tetramer-specific, IFN-gamma-producing CD8(+) T cells against each epitope. Vaccines incorporating a single epitope primed effector CTL able to kill male splenocytes in vitro and in vivo, and HY(Db)Uty-specific vaccination accelerated rejection of syngeneic male skin grafts. Priming against either epitope established long-term memory, expandable by injection of male cells. Expanded CD8(+) T cells remained specific for the priming HY epitope, with responses to the second suppressed. To investigate vaccine performance in a tolerized repertoire, male mice were vaccinated with the fusion constructs. Strikingly, this also generated epitope-specific IFN-gamma-producing CD8(+) T cells with cytotoxic function. However, numbers and avidity were lower than in vaccinated females, and vaccinated males failed to reject CFSE-labeled male splenocytes in vivo. Nevertheless, these findings indicate that DNA fusion vaccines can mobilize CD8(+) T cells against endogenous minor H Ags, even from a profoundly tolerized repertoire. In the transplantation setting, vaccination of donors could prime and expand specific T cells for in vivo transfer. For patients, vaccination could activate a potentially less tolerized repertoire against similar Ags that may be overexpressed by tumor cells, for focused immune attack.